Manifold for two-cycle crankcase compression engines



Jan. 18, 1949. w y 2,459,594

MANIFOLD FOR TWO-CYCLE CRANKCASE COMPRESSION ENGINES Filed Jan. 2, 1946 3 Sheets-Sheet l INVENTOR Jay W Jm/fl;

Jan. 18, 1949. J. w. SMITH MANIFOLD FOR TWO-CYCLE CRANKCASE COMPRESSION ENGINES I5 Sheets-Sheet 3 Filed Jan. 2, 1946 INVENTQR day 1446/77/27? Patented Jan. 18, 1949 UNITED MANIFOLD FOR TWO-CYCLE ORANKCASE COMPRESSION ENGINES Jay W. Smith, Algonae, Mlch., assignor to Chris-Craft Corporation, Algonac, Mich., a corporation of Delaware Application January 2, 1946, Serial No. 638,642

9 Claims. (Cl. 123-73) This invention relates generally to internal combustion engines and refers more particularly to improvements in fuel mixture intake manifolds for use in connection with two-cycle internal combustion engines.

One of the principal objects of this invention is to provide a small compact intake manifold capable of being readily installed on a multicylinder two-cycle internal combustion engine for supplying fuel mixture to at least two of the cylinders in proper timed relation.

Another object of this invention is to provide an intake manifold having means coacting with a part of the engine for separating the fuel mixture intake space adjacent one cylinder of the engine from a corresponding intake space adjacent another cylinder of the engine and having a fuel mixture intake passage equipped with discharge ports which respectively communicate with the spaces at opposite sides of the separating means.

Still another object of this invention is to provide an intake manifold of the type set forth in the preceding paragraph having reed type valves normally closing the discharge ports and movable to open the ports in response to movement of the pistons in the cylinders on their respective suction strokes.

A further object of this invention is to provide an intake manifold having a fuel intake passage formed with a venturi in advance of the discharge ports and having deflecting means for directing uniform quantities of fuel mixture from the venturi to the discharge ports.

A still further object of this invention is to provide an intake manifold having provision for scavenging raw fuel from the engine and for returning this fuel to the fuel mixture passage in the manifold.

Still another object of the present invention is to provide an intake manifold wherein the fuel mixture passage respectively communicates with adjacent cylinders of the engine through a plurality of discharge ports which are independently controlled by reed type valves carried by the manifold. This arrangement is advantageous in certain installations, because it not only tends to provide increased atomization of the fuel mixture, but also permits using smaller reed type valves, which tends to improve slow speed operation, because less vacuum pull is required to open the smaller valves.

A further object of this invention is to provide a manifold having means controlled by the reed valves for introducing a restricted quantity of air v 2 from the atmosphere directly into the engine when desired.

The foregoing as well as other objects will be made more apparent as this description proceeds. especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a fragmentary side elevation, partly in section, of an internal combustion engine equipped with a manifold construction in accordance with this invention;

Figure 2 is a plan view of the manifoldshown in Figure 1;

Figure 3 is an elevation of the manifold shown in Figure 2;

Figure 4 is a sectional view taken substantially on tehe plane indicated by the line 4-4 of Figure Figure 5 is a plan view of a modified form of manifold;

Figure 6 is a sectional view taken on the plane indicated by the line 6-6 of Figure 5;

Figure 7 is a plan view of still another embodiment of this invention;

Figure 8 is an elevation of the manifold shown in Figure '7; and

Figure 9 is a sectional view taken on the plane indicated by the line 9-9 of Figure 8.

In Figure 1 of the drawings, I have illustrated a part of a multicylinder, two-cycle internal combustion engine comprising a cylinder block i 0 and a casing II. The cylinder block l0 and the case Ii are formed separately from each other and are secured together by suitable studs, now shown herein. The case II and the adjacent portion of the cylinder block in are fashioned to cooperate with one another in forming three main bearings for the crankshaft l2. The top bearing is indicated by the reference character I! and the bottom bearing is designated by the numeral \l 9. The intermediate bearing is indicated by the reference character 20 and supports the crankshaft I 2 between the two cranks 2| and 22.

The cylinder block I0 is further fashioned to form adjacent cylinders 22 and 23. The inner ends of the cylinders communicate directly with the interior of the crankcasing indicated in Figure l of the drawings by the reference character 24 and the outer end portions of the cylinders also communicate with the interior of the crankcasing through a passage which extends from the crankcasingto suitable intake ports formed in the cylinders intermediate the ends of the latter. This arrangement is conventional in two cycle internal combustion engines and is not shown herein. Also not shown are suitable exhaust ports formed in the cylinders diametrically opposite the intake ports. Both the intake and exhaust ports are controlled by pistons 25, respectively slidably supported in the cylinders. The pistons are respectively connected to the cranks 2| and 22 by connecting rods 26.

In accordance with conventional practice, fuel mixture is supplied to the cylinders from the crankcasing 24 upon movement of the pistons on their suction strokes. In this connection, it is pointed out that the cranks are located 180 out of phase, so that one of the pistons moves inwardly on its suction stroke, while the other piston is moved outwardly on its compression stroke.

Fuel mixture is supplied to the crankcasing 24 by means of a carburetor 21 and an intake manifold 28. The carburetor may be of any accepted design and, accordingly, is not shown in detail herein. The intake manifold 28 shown in Figures 1 to 4 inclusive comprises a cylindrical body 29 and a projection 30. The cylindrical body 29 has a pressed fit in a bore 3| formed in the wall 32 of the case M and is provided with a radially outwardly extending annular flange 33 at the outer end thereof. The flange 33 abuts the adjacent wall 32 of the case M and is clamped against the latter by means of a pair of. studs 34, which are anchored in the intermediate bearing in a manner not shown herein. A suitable gasket 35 may be' provided between the inner face of the flange 33 and the wall 32 of the case to form a seal around the manifold.

As shown particularly in Figures 2 to 4 inclusive, the projection 30 extends diametrically of the cylindrical portion 29 and projects into the crankcasing 24. The inner surface 36 of the projection is formed perfectly flat and contacts a corresponding flat surface 31 on the intermediate bearing. As a result, the projection 30 cooperates with the intermediate bearing 2|] to divide the crankcasing 24 into two chambers 38 and 39 which respectively communicate with the inner ends of the two cylinders. Owing to the nature of the surface to surface contact between the projection and intermediate main bearing, a sufiiciently fluid-tight seal is provided without the necessity of employing gaskets and the like.

The cylindrical body portion of the manifold is formed with an axially extending bore 4|! shaped to form a Venturi and communicating at the outer end with the fuel mixture supply passage of the carburetor 21. The inner end of the Venturi passage 4|] communicates with opposed ports 4| and 42 respectively formed in the top and bottom walls of the projection. It follows from the above that the Venturi passage 40 communicates with the chambers 38 and 39 in the crankcasing 24.

The outlet or discharge ports 4| and 42 are normally closed by reed type valves 43 and 44. These valves are in the form of flat spring-metal strips and are respectively secured at corresponding ends to the top and bottom walls of the projection 30 by means of fastener elements 45. The free end portions of the valves respectively extend over the ports 4| and 42 to close the latter. The nature of these valves is such that they are opened by the suction created during outward movement of the pistons and the extent of opening of the valves may be limited by rigid backing members 46 which are respectively secured to opposite walls of the projection 30 by the fastener elements 45.

The fuel mixture flowing from the carburetor through the Venturi passage 40 is approximately equally divided between the two ports 4| and 42 by a partition or deflector 41. The deflector is substantially V-shaped in cross-section and projects transversely of the delivery end of the Venturi passage 40 between the discharge ports and the apex of the deflector occupies a plane including the axis of the Venturi passage. As a result, the deflector tends to direct the same amount of fuel mixture to both cylinders of the engine and thereby improves the fuel distribution characteristics of the engine.

In internal combustion engines operated on the two-cycle principle, it is customary to mix the lubricant with the fuel. As this mixture is admitted to the crankcase through either one or the other of the manifold discharge ports, raw fuel and libricant in the mixture has a tendency to drop out of suspension. The raw fuel falling out of suspension in the fuel mixture admitted to the chamber 33 is accumulated on the surfaces 48 and 49. This raw fuel is conducted by passages 50 to an-annular groove 5| formed in the periphery of the liner for the intermediate bearing 28 and is discharged back into the Venturi passage 43 through a passage 52 formed in the V-shaped deflector 41 of the manifold. The passage 52 is reduced at the delivery end thereof in order to meter the amount of raw fuel admitted to the Venturi passage soas not to appreciably change the proportions ofthe mixture flowing through the Venturi passage.

The raw fuel falling out of suspension in the fuel mixture admitted to the chamber 29 in the crankcasing is accumulated on the surface 54 immediately below the lowermost piston 25 and is conducted by a passage 55 to an annluar groove 56 formed in the liner for the bottom main bearing IS. The annular groove 56 communicates with the upper end of a longitudinally extending groove 57 also formed in the periphery of the lower bearing line and which, in turn, communicates with a Well 58 arranged to also collect raw fuel that may drop out of suspension from the fuel mixture admitted to the chamber 39. In addition, the lower end portion of the groove 51 communicates with the lower end of a passage 60 having the upper end communicating with the Venturi passage 40 through a restriction 6|. The arrangement is such that raw fuel accumulated on the surfaces 54 and in the well 58 is returned to the Venturi passage 40 for readmission to the crankcasing 24. In this connection, it is pointed out that the flow of fuel mixture through the venturi creates a suction in the passage 60 which assists in drawing the raw fuel from the portions of the crankcase described to the Venturi passage.

If desired, a second passage 66 is formed in the manifold diametrically opposite the passage 60. The outer end of this passage communicates with an annular groove 61 formed in the inner surface of the liner for the top main bearing. The groove 61 tends to collect raw fuel and lubricant escaping along the crankshaft and the passage 66 enables returning this fuel to the Venturi passage 40. The delivery end 68 of the passage 66 is also restricted to limit the amount of raw fuel returned to the Venturi passage, so that the balance of the fuel mixture is not seriously disturbed or changed.

The embodiment of the invention shown in;

as to enable forming a plurality of discharge ports II and 12 in each of the top and bottom sides respectively of the projection. Each of the discharge openings II is controlled by a reed type valve 13 secured to the top surface of the projection III in the same manner as the valves 43. The discharge openings 12 are also independently controlled by reed type valves 14 secured to the bottom surface of the projection in the same manner as the valves 46 in the first described form of the invention. By directing the fuel mixture through a plurality of discharge ports, a more thorough atomization of the fuel mixture is accomplished and the distribution of this fuel mixture is enhanced. Also, smaller reed type valves may be used with the result that less suction or vacuum pull is required to open the valves and this is particularly advantageous during slow speed operation. The remaining structure of the manifold shown in Figures 5 and 6 is similar to the manifold previously described and the same reference characters are employed to indicate corresponding parts.

The embodiment of the invention shown in Figures '7 to 9 inclusive illustrates a manifold similar to the manifold 30, except that the annular portion 80 is tapered and provision is made for conducting a restricted volume of air from the atmosphere directly into the engine. The tapered portion 80 is adapted to fit in a correspondingly tapered bore formed in the case of the engine and thereby not only facilitates installation of the manifold, but also permits the latter to be readily removed when desired. When using the tapered feature, it may be necessary to provide a gasket between the end surface 36 on the projection 30 and the adjacent surface of the intermediate main bearing. This gasket is indicated by the reference character BI and the surface 36 is fashioned to form a seat for this gasket. It will be noted that the asket has an annular portion which surrounds the bore or passage 52 in the deflector 41 and provision is made to prevent obstructing the passage 52 by the gasket when the latter is placed under compression. As shown particularly in Figure 9, the passage 52 is somewhat greater in diameter than the corresponding passage set forth in connection with the first described form of the invention and a tube 82 is sleeved in the passage. The tube projects through the annular portion of the gasket and acts as a guard to prevent any part of the gasket from obstructing the passage 52.

As shown particularly in Figure 8 of the drawings, a pair of ports 83 and 84 are respectively formed in the top and bottom surfaces of the projection 30 and are positioned to be controlled by the reed type valves 43 and 44. The ports 83 and 84 respectively communicate with passages 85 which open through the radial flange 33. The outer ends of the passages 85 are threaded for respectively receiving jets 86 having restricted passages ll'l therethrough. The passages 81 communicate with the ports 83 and 84 to supply a restricted quantity of air from the atmosphere directly to either the chamber 38 in the engine or the engine 39, depending upon which of the reed valves is open. The jets may be readily interchanged for jets having restricted passages of different size, so that varying quantities of air may be admitted to the engine.

What I claim as my invention is:

1. An intake manifold for internal combustion engines, comprising a body attachable to a part of an internal combustion engine and having a portion adapted to extend into a part of'the engine, said portion having a passage closed at the inner end and extending through the outer side of the body for connection with a fuel mixture supply, discharge ports at opposite sides oi the projecting portion communicating with the passage, and reed type valve members respectively secured to opposite sides of the projecting portion in operative relation to the ports for controlling the flow of fuel mixture through said ports.

2. An intake manifold for internal combustion. engines, comprising a body attachable to a part of an internal combustion engine and having a passage therethrough for fuel mixture, a projection on the body having discharge ports at opposite sides respectively communicating with the passage, means extending into the passage for defleeting uniform quantities of fuel mixture to the discharge ports at opposite sides of the projection, and reed type valve members respectively secured to opposite sides of the projection and having portions extending over the discharge ports for controlling the latter.

3. An intake manifold for an'internal combustion engine having cylinders and having a space adjacent the cylinders for fuel mixture, said manifold comprising a body attachable to a part of the interna1 combustion engine and having a passage therethrough for fuel mixture, a projection on the body extending into the fuel mixture space between adjacent cylinders of the engine for dividing said space into two chambers and having discharge ports at opposite sides thereof respectively communicating with the fuel mixture passage, and reed type valve members respectively secured to opposite sides of the projection and normally closing said discharge ports.

4. An intake manifold for internal combustion engines, comprising a body attachable to a part of an internal combustion engine and having a Venturi-shaped passage therethrough for fuel mixture, a projection on the body having discharge ports at opposite sides respectively communicating with the fuel mixture passage and reed type valve members respectively secured to opposite sides of the projection and having portions normally closing the discharge ports.

5. An intake manifold for internal combustion engines, comprising a body having a cylindrical portion adapted to fit in a bore formed in a part of an internal combustion engine'and having a passage therethrough for fuel mixture, a projection extending diametrically across the cylindrical portion and projecting inwardly from the inner face of the cylindrical portion, said projection having a plurality of discharge ports in each of opposite sides thereof respectively communicating with the passage, and reed type valves corresponding in number to the number of discharge ports and respectively secured to opposite sides of the projection for independently controlling the flow of fuel mixture through the discharge ports.

6. An intake manifold for internal combustion engines, comprising a body attachable to a part of an internal combustion engine and having a passage therethrough for fuel mixture, a projection extending from the body and having discharge ports at opposite sides respectively communicating with the fuel mixture passage, a, deflector carried by the projection between the discharge ports and shaped to direct uniform quantities of fuel mixture to the discharge ports, a passage extending through the deflector for returning raw fuel mixture to said passage, and reed type valve members respectively secured to 7 opposite sides of the projection and having portions normally closing said discharge ports.

7. An intake manifold for internal combustion engines, comprising a body attachable to a part of an internal combustion engine and having a Venturi-shaped passage therethrough for fuel mixture, 2. projection extending from the body and having discharge ports at opposite sides respectively communicating with the delivery end of the fuel mixture passage, restricted passages formed in the body and communicating with the venturi intermediate the ends thereof for returning raw fuel to the Venturi-shaped passage, and valve members respectively secured to opposite sides of the projection for controlling the flow of fuel mixture through said ports.

8. An intake manifold for internal combustion engines,- comprising a body attachable to a part of an internal combustion engine and having a passage therethrough for fuel mixture, a partition extending from the body and having discharge ports at opposite sides respectively communicating with the passage, additional ports respectively formed in opposite sides of the projection and communicating with the atmosphere, and reed type valve members respectively secured to opposite sides of the projection and having portions for controlling the flow of fuel mixture through the discharge ports and for controlling the passage of air through the other of said ports.

9. An intake manifold for internal combustion engines, comprising a body attachable to a part JAY W. SMITH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 876,880 Johnson Jan. 14, 1908 1,121,153 Woolf Dec. 15, 1914 1,130,526 Taurin Mar. 2, 1915 1,407,586 Setz Feb. 21, 1922 1,845,702 Evinrude Feb. 16, 1932 2,079,571 Johnson May 4, 1937 2,397,457 Krezke Mar. 26, 1946 FOREIGN PATENTS Number Country Date 125,173 Great Britain 1919 

